Update momentjs to 2.29.4

[yubiuser]

What does this PR aim to accomplish?:

Update momentjs to the latest version 2.29.4

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Moment considers itself

We now generally consider Moment to be a legacy project in maintenance mode. It is not dead, but it is indeed done.

https://momentjs.com/docs/

I looked for a replacement (e.g. luxon) which moment recommends, but failed at daterangepicker which needs momentjs internally. daterangepicker itself also looks like a "legancy project" (last release 2 years ago), but I could not find a suitable replace with the same feature set.

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2. I have commented my proposed changes within the code and I have tested my changes.
3. I am willing to help maintain this change if there are issues with it later.
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5. I have squashed any insignificant commits. (git rebase)

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[DL6ER]

I don't have any issues with "this project is done" - it just offers anything you'd want. I also interpret this as: "If there are serious security issues, we will fix them"

Again, testing showed no obvious oddities - ready for merging into devel IMO